by Jette Eva Madsen, 07.12.2001.

More than a year has now elapsed since we heard the last news about the x-coloured cats. Last time was after a test mating between a Forest Cat that was believed to be cinnamon and a fawn Somali produced one blackticked tabby and one blueticked tabby kitten. That test mating proved the Forest Cat was not cinnamon.

Since then we have heard only very little. Cats are still registered as if they were possibly cinnamon or fawn and breeders still talk about those colours.

All the time I have thought:  What is it then? There is of course always a chance that it is a new mutation, but the chance is much greater that it is something we already know.

Could those colours be caused by the action of the dilute modifier gene?

This far the dilute modifier gene is poorly understood, but I will try to explain a bit about the gene.

  • The gene is known mainly from the Siamese and Oriental Shorthair.
  • The dilute modifier has been present in Siamese for many years. Certainly since the tabby points appeared. 
  • It was probably introduced via one of the outcross matings that also introduced the tabby pattern into the Siamese.
  • The gene is dominant.
  • The effect of the gene is to slightly close up the pigment granules so that less light pass through the hair shaft and the colour get a more brown tinge.
  • The colour is slow to develop.
  • It can be very difficult to distinguish a caramel coloured cat from a blue, lilac or chocolate.

What does the colours look like?

In Siamese / Oriental they look like this:

One of the characteristics of the blue based caramel tabbies is a metallic, aluminium like sheen, which is particularly visible across the neck and top of head. It is not so apparent in the blue self form.

  Name Expression
Blue self + dilute modifier Caramel

Coat colour like a dark lilac or warm-toned blue. Nose leather mauve or slightly darker than lilac.

Red/cream + dilute modifier Apricot Coat colour very hot cream. The tone is muted. Other describe it as a dark cream with a silver sheen
Blue tabby + dilute modifier Caramel tabby

Almost grey-brown with a metallic sheen on the scarab, sometimes on the leg bracelets and tail rings. Other describe it as a darker version of lilac, with a silvery sheen developing with time

Paw pads metallic sheen
Black self + dilute modifier ? ?
Black tabby + dilute modifier ? ?
Smoke + dilute modifier ? ?
Silver + dilute modifier ? ?

It is not known what the colours look like in long-haired cats, but it is known that the length of the hair effect the influence the overall effect of the dilution modifier on the colour.

Based on the observations made on Siamese it is believed that the gene effect only diluted colours. Because of the effect of the gene on the pigment granules it is likely, however,  that lighter toned black tabbies, silver tabbies and smokes are also influenced.

Does this correspond with the colours seen on Forest Cats?

The difficulties in distinguishing between caramel and other colours and the comments that many caramel kittens are registered as blue, lilac or chocolate could explain why the Forest Cats are registered and reregistered as blue, lilac cinnamon, etc.

The metallic sheen seen on some of these cats can also be found in some of the Forest Cats.

The colour of the paw pads can also be seen in Forest Cats

What cannot be accounted for with the dilute modifier is the fact that non-diluted colours should not be effected. But knowing that the dilute modifier has effect on different genes from different locus on the chromosomes in the very short haired Siamese (O, b, d) lead me to ask if:

The dilute modifier has effect on all the colour genes?

The effect of the dilute modifier is more pronounced when the hair is longer?

The effect of the gene is more pronounced the lighter the base colour?

The test:

The test matings necessary in order to investigate these questions may prove to be more difficult than the test mating performed with a fawn Somali.

The caramel and apricot Siamese/Orientals are not found in large numbers in FIFe and the Norwegian Forest Cats are mainly found in FIFe. Secondly, more than one mating is necessary since most Siamese/Orientals are homozygotic for the short hair gene. Therefore, at least two generations are needed in order to test the effect of the genes on long hair.

For examples on how cats of these "X-Colors" look, please refer to the "Gallery"-part of